To assign new skills:
1. Press K or select the special notification that pops up on your screen when skill upgrades are available.
2. Click on the tab labeled Current Class at the top of your class window. [http://img101.imageshack.us/img101/9908/currentclass.jpg
3. On the left side, choose Reg. Skills or Class Skills
4. Click Upgrade beside the skill you wish to upgrade! The new level of the skill will update on your skill bars, so there is no need to replace it after upgrading.
How do I add skills to my hotbars?
1. Press K to open your class window.
2. Click the tab labeled Current Class.
3. On the left side, choose Reg. Skills or Class Skills.
4. Click the skill once to select it, then click on your hotbar where you want to place your skill.
Now you can use the corresponding hotkey or right-click your skill to use it with ease!